JAKARTA — Anisah Firdaus Bandu’s mother called her in tears from her hometown of Palu on Friday evening when a magnitude 7.5 earthquake jolted the island of Sulawesi in eastern Indonesia.

Since then, with cellphone towers and other infrastructure damaged by the quake and an ensuing tsunami, Anisah hasn’t heard from her parents, who are among thousands believed unaccounted for in the disaster that has left at least 800 people dead, officials said Sunday.

“My mother cried a lot, she tried to pick up my father at his office,” said Anisah, a civil servant in Jakarta, the capital.

“I really tried hard to reach them till now but I can’t.”

As anxious relatives tried to place phone calls in vain and clamored to board military or relief flights to Palu, a town of some 380,000 people, emergency crews struggled to reach the worst affected areas, including a string of coastal towns that remained cut off by washed-out roads and downed communication lines.

Indonesia’s national disaster agency said the official death toll had more than doubled overnight, to 832 people, but nearly all of those were in Palu. Officials warned that the toll was likely to rise as relief workers reach major towns such as Donggala, with a population of around 300,000 that is normally a half-hour drive north of Palu.

“The death toll will increase but I cannot say [by] how much,” Sutopo Nugroho, the disaster agency spokesman, told The Times in Jakarta.

With “catastrophic damage” in many areas, relief agencies were bracing for a large loss of life once teams could assess the effects in Donggala and other towns, said Tom Howells, program implementation director for Save the Children’s Jakarta office.

“Aid agencies and local authorities are struggling to reach several communities around Donggala…. We hold grave fears for many of the towns in this area,” Howells said in a press release.

Images aired on local TV and social media sites from Palu showed scenes of death and destruction: crumpled buildings and bridges surrounded by dead bodies, some covered in blankets, some with their clothes partly ripped off by the force of a tsunami that measured between five and 20 feet high.

Indonesian news media said dozens of people were trapped beneath toppled hotels and malls in Palu, an echo of scenes on the island of Lombok in August when a series of earthquakes killed more than 460 people.

An Associated Press reporter in Palu said that rescue workers were focusing on an eight-story hotel where on Saturday voices were heard calling for help from under the rubble. Officials estimated about 50 people were inside the hotel, but the cries for help were no longer heard by Sunday afternoon, the AP reported.

With roads into Palu blocked by landslides and the town’s airport damaged, getting teams of relief workers from elsewhere in Indonesia to the disaster zone was proving difficult, delaying timely assistance to survivors and the arrival of heavy equipment that could save the people trapped inside downed buildings.

Officials said they would deliver some assistance via Makassar, the biggest city on Sulawesi, an island of about 18 million people roughly the size of Florida. Makkasar lies at the southern end of the island, a 12-hour drive from Palu.

Dozens of strong aftershocks have struck Palu, where many fearful residents were reluctant to reenter their homes, said Rafiq Anshori, head of the Indonesian Red Cross’s disaster preparedness division. He spoke by phone from Palu, where some communications had been restored by Sunday evening.

“Many road[s], houses, other facilities are broken,” he said. “People are finding it difficult to get food, water, fuel.”

Indonesia, an expansive archipelago nation comprising more than 17,000 islands, lies in an earthquake prone area known as the “Ring of Fire.” Several devastating earthquakes have struck here in recent years, the deadliest a magnitude 9.1 temblor in 2004 that unleashed a tsunami across the Indian Ocean, killing 230,000 people.

Imade Boby, a 35-year-old Jakarta resident, said he hasn’t been able to reach his family members in Palu since the quake.

“My mother my father are there,” he said on Sunday afternoon, his voice quivering. “Until now I never get updated information.” But by 11pm the same night, Mr Imade finally heard from his missing parents, via one of his brothers who lives in Sulawesi and who made it to Palu by Sunday. “Finally I found my family in Palu and thank God they are in good condition,” Imade said in a text message.